I have a trip planned for January 2020 to the Azores and Lisbon. I plan on bringing my M240 with 35 Cron, and 28 Ultron VM. I want to do some landscape and seascape images and would like to get a wide or ultra wide angle lens. I'm looking for suggestions or user experience on what is available. Right now my top choices are the Voigtlander 12mm f5.6 (which i can use on my Xpro2 as well) or Voigtlander 15mm f4.5 which will be cheaper but won't be useful on my crop sensor (I already have that focal length covered).
My other option would be the Leica 21mm f3.4 SEM... which I hear is an excellent lens but would require me to sell some gear fast to afford it.
Anyone have any other suggestions or can give me insight on their experience with the choices i have listed?